Add support for Dotty about scala-swing HOT 6 CLOSED

// object Action
    trait Wrapper extends Action.Trigger {
      def peer: javax.swing.JComponent {
        def addActionListener(a: ActionListener): Unit
        def removeActionListener(a: ActionListener): Unit
        def setAction(a: javax.swing.Action): Unit
        def getAction(): javax.swing.Action // note: must keep empty parentheses for Java compatibility
      }

      private var _action: Action = Action.NoAction
      def action: Action = _action
      def action_=(a: Action): Unit = { _action = a; peer.setAction(a.peer) }